/*-
 * Copyright 2003-2005 Colin Percival
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted providing that the following conditions 
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#if 0
__FBSDID("$FreeBSD: src/usr.bin/bsdiff/bsdiff/bsdiff.c,v 1.1 2005/08/06 01:59:05 cperciva Exp $");
#endif

#include <sys/types.h>

#include "bzip2/bzlib.h"
#include <err.h>
#include <fcntl.h>
#include "bs.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define MIN(x,y) (((x)<(y)) ? (x) : (y))

static void split(off_t *I,off_t *V,off_t start,off_t len,off_t h)
{
	off_t i,j,k,x,tmp,jj,kk;

	if(len<16) {
		for(k=start;k<start+len;k+=j) {
			j=1;x=V[I[k]+h];
			for(i=1;k+i<start+len;i++) {
				if(V[I[k+i]+h]<x) {
					x=V[I[k+i]+h];
					j=0;
				};
				if(V[I[k+i]+h]==x) {
					tmp=I[k+j];I[k+j]=I[k+i];I[k+i]=tmp;
					j++;
				};
			};
			for(i=0;i<j;i++) V[I[k+i]]=k+j-1;
			if(j==1) I[k]=-1;
		};
		return;
	};

	x=V[I[start+len/2]+h];
	jj=0;kk=0;
	for(i=start;i<start+len;i++) {
		if(V[I[i]+h]<x) jj++;
		if(V[I[i]+h]==x) kk++;
	};
	jj+=start;kk+=jj;

	i=start;j=0;k=0;
	while(i<jj) {
		if(V[I[i]+h]<x) {
			i++;
		} else if(V[I[i]+h]==x) {
			tmp=I[i];I[i]=I[jj+j];I[jj+j]=tmp;
			j++;
		} else {
			tmp=I[i];I[i]=I[kk+k];I[kk+k]=tmp;
			k++;
		};
	};

	while(jj+j<kk) {
		if(V[I[jj+j]+h]==x) {
			j++;
		} else {
			tmp=I[jj+j];I[jj+j]=I[kk+k];I[kk+k]=tmp;
			k++;
		};
	};

	if(jj>start) split(I,V,start,jj-start,h);

	for(i=0;i<kk-jj;i++) V[I[jj+i]]=kk-1;
	if(jj==kk-1) I[jj]=-1;

	if(start+len>kk) split(I,V,kk,start+len-kk,h);
}

struct bsdiff_stream
{
    void* opaque;

    void* (*malloc)(size_t size);
    void (*free)(void* ptr);
    int (*write)(struct bsdiff_stream* stream, const void* buffer, int size);
};

static void qsufsort(off_t *I,off_t *V,const u_char *old,off_t oldsize)
{
    off_t buckets[256];
    off_t i,h,len;

    for(i=0;i<256;i++) buckets[i]=0;
    for(i=0;i<oldsize;i++) buckets[old[i]]++;
    for(i=1;i<256;i++) buckets[i]+=buckets[i-1];
    for(i=255;i>0;i--) buckets[i]=buckets[i-1];
    buckets[0]=0;

    for(i=0;i<oldsize;i++) I[++buckets[old[i]]]=i;
    I[0]=oldsize;
    for(i=0;i<oldsize;i++) V[i]=buckets[old[i]];
    V[oldsize]=0;
    for(i=1;i<256;i++) if(buckets[i]==buckets[i-1]+1) I[buckets[i]]=-1;
    I[0]=-1;

    for(h=1;I[0]!=-(oldsize+1);h+=h) {
        len=0;
        for(i=0;i<oldsize+1;) {
            if(I[i]<0) {
                len-=I[i];
                i-=I[i];
            } else {
                if(len) I[i-len]=-len;
                len=V[I[i]]+1-i;
                split(I,V,i,len,h);
                i+=len;
                len=0;
            };
        };
        if(len) I[i-len]=-len;
    };

    for(i=0;i<oldsize+1;i++) I[V[i]]=i;
}

static off_t matchlen(const u_char *old,off_t oldsize,const u_char *new,off_t newsize)
{
    off_t i;

    for(i=0;(i<oldsize)&&(i<newsize);i++)
        if(old[i]!=new[i]) break;

    return i;
}

static off_t search(const off_t *I,const u_char *old,off_t oldsize,
                      const u_char *new,off_t newsize,off_t st,off_t en,off_t *pos)
{
    off_t x,y;

    if(en-st<2) {
        x=matchlen(old+I[st],oldsize-I[st],new,newsize);
        y=matchlen(old+I[en],oldsize-I[en],new,newsize);

        if(x>y) {
            *pos=I[st];
            return x;
        } else {
            *pos=I[en];
            return y;
        }
    };

    x=st+(en-st)/2;
    if(memcmp(old+I[x],new,MIN(oldsize-I[x],newsize))<0) {
        return search(I,old,oldsize,new,newsize,x,en,pos);
    } else {
        return search(I,old,oldsize,new,newsize,st,x,pos);
    };
}
static void offtout(off_t x,u_char *buf)
{
    off_t y;

    if(x<0) y=-x; else y=x;

    buf[0]=y%256;y-=buf[0];
    y=y/256;buf[1]=y%256;y-=buf[1];
    y=y/256;buf[2]=y%256;y-=buf[2];
    y=y/256;buf[3]=y%256;y-=buf[3];
    y=y/256;buf[4]=y%256;y-=buf[4];
    y=y/256;buf[5]=y%256;y-=buf[5];
    y=y/256;buf[6]=y%256;y-=buf[6];
    y=y/256;buf[7]=y%256;

    if(x<0) buf[7]|=0x80;
}

static off_t writedata(struct bsdiff_stream* stream, const void* buffer, off_t length)
{
    off_t result = 0;

    while (length > 0)
    {
        const int smallsize = (int)MIN(length, INT_MAX);
        const int writeresult = stream->write(stream, buffer, smallsize);
        if (writeresult == -1)
        {
            return -1;
        }

        result += writeresult;
        length -= smallsize;
        buffer = (u_char*)buffer + smallsize;
    }

    return result;
}

struct bsdiff_request
{
    u_char* old;
    off_t oldsize;
    u_char* new;
    off_t newsize;
    struct bsdiff_stream* stream;
    off_t *I;
    u_char *buffer;
};

static int bsdiff_internal(const struct bsdiff_request req)
{
    off_t *I,*V;
    off_t scan,pos,len;
    off_t lastscan,lastpos,lastoffset;
    off_t oldscore,scsc;
    off_t s,Sf,lenf,Sb,lenb;
    off_t overlap,Ss,lens;
    off_t i;
    u_char *buffer;
    u_char buf[8 * 3];

    if((V=req.stream->malloc((req.oldsize+1)*sizeof(off_t)))==NULL) return -1;
    I = req.I;

    qsufsort(I,V,req.old,req.oldsize);
    req.stream->free(V);

    buffer = req.buffer;

    /* Compute the differences, writing ctrl as we go */
    scan=0;len=0;pos=0;
    lastscan=0;lastpos=0;lastoffset=0;
    while(scan<req.newsize) {
        oldscore=0;

        for(scsc=scan+=len;scan<req.newsize;scan++) {
            len=search(I,req.old,req.oldsize,req.new+scan,req.newsize-scan,
                       0,req.oldsize,&pos);

            for(;scsc<scan+len;scsc++)
                if((scsc+lastoffset<req.oldsize) &&
                   (req.old[scsc+lastoffset] == req.new[scsc]))
                    oldscore++;

            if(((len==oldscore) && (len!=0)) ||
               (len>oldscore+8)) break;

            if((scan+lastoffset<req.oldsize) &&
               (req.old[scan+lastoffset] == req.new[scan]))
                oldscore--;
        };

        if((len!=oldscore) || (scan==req.newsize)) {
            s=0;Sf=0;lenf=0;
            for(i=0;(lastscan+i<scan)&&(lastpos+i<req.oldsize);) {
                if(req.old[lastpos+i]==req.new[lastscan+i]) s++;
                i++;
                if(s*2-i>Sf*2-lenf) { Sf=s; lenf=i; };
            };

            lenb=0;
            if(scan<req.newsize) {
                s=0;Sb=0;
                for(i=1;(scan>=lastscan+i)&&(pos>=i);i++) {
                    if(req.old[pos-i]==req.new[scan-i]) s++;
                    if(s*2-i>Sb*2-lenb) { Sb=s; lenb=i; };
                };
            };

            if(lastscan+lenf>scan-lenb) {
                overlap=(lastscan+lenf)-(scan-lenb);
                s=0;Ss=0;lens=0;
                for(i=0;i<overlap;i++) {
                    if(req.new[lastscan+lenf-overlap+i]==
                       req.old[lastpos+lenf-overlap+i]) s++;
                    if(req.new[scan-lenb+i]==
                       req.old[pos-lenb+i]) s--;
                    if(s>Ss) { Ss=s; lens=i+1; };
                };

                lenf+=lens-overlap;
                lenb-=lens;
            };

            offtout(lenf,buf);
            offtout((scan-lenb)-(lastscan+lenf),buf+8);
            offtout((pos-lenb)-(lastpos+lenf),buf+16);

            /* Write control data */
            if (writedata(req.stream, buf, sizeof(buf)))
                return -1;

            /* Write diff data */
            for(i=0;i<lenf;i++)
                buffer[i]=req.new[lastscan+i]-req.old[lastpos+i];
            if (writedata(req.stream, buffer, lenf))
                return -1;

            /* Write extra data */
            for(i=0;i<(scan-lenb)-(lastscan+lenf);i++)
                buffer[i]=req.new[lastscan+lenf+i];
            if (writedata(req.stream, buffer, (scan-lenb)-(lastscan+lenf)))
                return -1;

            lastscan=scan-lenb;
            lastpos=pos-lenb;
            lastoffset=pos-scan;
        };
    };

    return 0;
}


int bsdiff(u_char* old, off_t oldsize, u_char* new, off_t newsize, struct bsdiff_stream* stream)
{
    int result;
    struct bsdiff_request req;

    if((req.I=stream->malloc((oldsize+1)*sizeof(off_t)))==NULL)
        return -1;

    if((req.buffer=stream->malloc(newsize+1))==NULL)
    {
        stream->free(req.I);
        return -1;
    }

    req.old = old;
    req.oldsize = oldsize;
    req.new = new;
    req.newsize = newsize;
    req.stream = stream;

    result = bsdiff_internal(req);

    stream->free(req.buffer);
    stream->free(req.I);

    return result;
}

static int bz2_write(struct bsdiff_stream* stream, const void* buffer, int size)
{
    int bz2err;
    BZFILE* bz2;

    bz2 = (BZFILE*)stream->opaque;
    BZ2_bzWrite(&bz2err, bz2, (void*)buffer, size);
    if (bz2err != BZ_STREAM_END && bz2err != BZ_OK)
        return -1;

    return 0;
}

int mydiff(int argc,char *argv[])
{
    int fd;
    int bz2err;
    u_char *old,*new;
    off_t oldsize,newsize;
    u_char buf[8];
    FILE * pf;
    struct bsdiff_stream stream;
    BZFILE* bz2;

    memset(&bz2, 0, sizeof(bz2));
    stream.malloc = malloc;
    stream.free = free;
    stream.write = bz2_write;

    if(argc!=4) errx(1,"usage: %s oldfile newfile patchfile\n",argv[0]);

    /* Allocate oldsize+1 bytes instead of oldsize bytes to ensure
        that we never try to malloc(0) and get a NULL pointer */
    if(((fd=open(argv[1],O_RDONLY,0))<0) ||
       ((oldsize=lseek(fd,0,SEEK_END))==-1) ||
       ((old=malloc(oldsize+1))==NULL) ||
       (lseek(fd,0,SEEK_SET)!=0) ||
       (read(fd,old,oldsize)!=oldsize) ||
       (close(fd)==-1)) err(1,"%s",argv[1]);


    /* Allocate newsize+1 bytes instead of newsize bytes to ensure
        that we never try to malloc(0) and get a NULL pointer */
    if(((fd=open(argv[2],O_RDONLY,0))<0) ||
       ((newsize=lseek(fd,0,SEEK_END))==-1) ||
       ((new=malloc(newsize+1))==NULL) ||
       (lseek(fd,0,SEEK_SET)!=0) ||
       (read(fd,new,newsize)!=newsize) ||
       (close(fd)==-1)) err(1,"%s",argv[2]);

    /* Create the patch file */
    if ((pf = fopen(argv[3], "w")) == NULL)
        err(1, "%s", argv[3]);

    /* Write header (signature+newsize)*/
    offtout(newsize, buf);
    if (fwrite("ENDSLEY/BSDIFF43", 16, 1, pf) != 1 ||
        fwrite(buf, sizeof(buf), 1, pf) != 1)
        err(1, "Failed to write header");


    if (NULL == (bz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)))
        errx(1, "BZ2_bzWriteOpen, bz2err=%d", bz2err);

    stream.opaque = bz2;
    if (bsdiff(old, oldsize, new, newsize, &stream))
        err(1, "bsdiff");

    BZ2_bzWriteClose(&bz2err, bz2, 0, NULL, NULL);
    if (bz2err != BZ_OK)
        err(1, "BZ2_bzWriteClose, bz2err=%d", bz2err);

    if (fclose(pf))
        err(1, "fclose");

    /* Free the memory we used */
    free(old);
    free(new);

    return 0;
}
